JPH01276639A - Pattern inspection - Google Patents

Abstract

PURPOSE:To improve both inspection efficiency and accuracy, by putting a pattern that is different from the pattern inspected on the top of the pattern inspected and comparing the two superposed patterns with each other. CONSTITUTION:A reference pattern 2 having a pattern that is different from the pattern 1 inspected is formed on a semiconductor substrate and the pattern inspected is formed by putting it on the top of the above reference pattern. Thus superposed pattern 3 is compared with other superposed pattern which is formed on the same semiconductor substrate through a pattern inspection device by image recognition. This approach improves the superposing accuracy of the pattern by image recognition and serves the purpose of performing the relative inspection of patterns with high accuracy.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a pattern inspection method in a lithography process in which a pattern is formed using a mask.

In the lithography process using conventional technology masks, if there are pattern defects, scratches, dirt, dust, etc. on the mask,
When the mask is transferred onto a semiconductor substrate, any pattern formed using the mask will have defects, reducing yield. In particular, reduction projection type exposure @
When a single defect is used, one defect on the mask appears as a common defect in all shots on one semiconductor substrate, significantly reducing the yield. In order to discover and remove the above defects, before forming a pattern on a semiconductor substrate on which semiconductor elements are to be formed, the pattern of the mask is transferred onto another flat semiconductor substrate and the formed pattern is inspected. things will be done. This inspection may be done manually, but the minimum line width is 1
Fine patterns on the order of micrometers are often inspected using automatic inspection equipment that detects patterns using reflected light. An automatic inspection device compares the same part of one chip with another chip, detects a difference in pattern, and displays it as a defect.

After automatic inspection, the position of the defect is confirmed by the pattern on the inspected semiconductor substrate, and the position of the defect on the mask is known.
Measures such as cleaning the mask are taken, and this test is repeated until the predetermined test standards are met. Thereafter, a pattern is formed on a semiconductor substrate on which a semiconductor element is to be formed, using a mask that satisfies the inspection criteria.

Problems to be Solved by the Invention Automatically detecting patterns formed on a flat semiconductor substrate using reflected light and superimposing and comparing them with patterns at the same location on another chip using image recognition. When performing inspection using a pattern inspection device, when there are many very simple repeating patterns, especially when the repeating units that make up the patterns are simple patterns, it is possible to use a pattern inspection device that uses distinctive images in the detected screen. Pattern overlay may fail, causing overlay errors on the entire screen, and many defects may be detected.

Device like this! When there are many defects detected by recognition (hereinafter referred to as pseudo defects), the defects detected by automatic pattern inspection equipment can be detected later by humans! ! There is a problem in that it takes a great deal of time to check, and mistakes such as overlooking original defects are made, which leads to a decrease in inspection efficiency and accuracy, and ultimately increases manufacturing costs.

Therefore, an object of the present invention is to provide a pattern inspection method that can solve the above problems.

Means for Solving the Problems In order to solve the above-mentioned problems, the pattern inspection method of the present invention forms a reference pattern having a pattern similar to the pattern to be inspected on a semiconductor substrate, and injects the pattern to be inspected into this reference pattern. In this method, two overlapping patterns are formed in an overlapping manner, and this overlapping pattern is compared with other overlapping patterns formed on the same semiconductor substrate using a pattern inspection device using image recognition.

According to the above inspection method, a reference pattern having a pattern different from the pattern to be inspected is superimposed on the pattern to be inspected to form a superimposed pattern, and by comparing such superimposed patterns, it is possible to detect whether the same mask Inspection is performed by comparing a plurality of patterns to be inspected formed thereon.

EXAMPLE An example of the pattern inspection method of the present invention will be described below with reference to the drawings.

Incidentally, FIG. 1 shows an example of a pattern 1 that is originally to be inspected (hereinafter referred to as a pattern to be inspected), and this pattern is a wiring pattern with a pitch of 3 μm and a line width of 1.5 μm. Further, a plurality of patterns to be inspected are formed on the same mask, and defects are discovered by comparing these patterns to be inspected.

First, an oxide film with a thickness of about 1000 μm is formed on a semiconductor substrate, and a photoresist is coated on this film with a thickness of about 1 μm. As shown in FIG. 2, a pattern different from pattern 1 to be inspected is formed. After exposing the reference pattern 2 using a wafer stepper or the like, it is developed. This reference pattern 2 is a contact hole pattern of 1.2 μm square and 1.5 μm square, and the chip size and chip pitch are the same as the pattern to be inspected 1 shown in FIG. This contact hole pattern has both an X direction component and a Y direction component. Next, using this resist pattern as a mask, the underlying oxide film is dry etched, and then the resist is removed. Next, photoresist was applied again to a thickness of about 1 μm on this semiconductor substrate with the etching pattern, and the pattern to be inspected 1 shown in FIG. 1 was previously formed using a wafer stepper or the like. After being superimposed on the etching pattern and exposed, it is developed. At this time, the pattern formed on the semiconductor substrate becomes a superimposed pattern 3 in which the pattern to be inspected 1 and the reference pattern 2 overlap, as shown in FIG.

Of course, the number of overlapping patterns 3 formed at this time is the same as the number of inspected patterns 1 formed on the same mask. After that, this semiconductor substrate is irradiated with halogen lamp light to be blued with a wavelength of 400 nm to 800 nm.
By detecting one of the overlapping patterns 3 using reflected light around 550 nm in a range of m, for example, and matching this overlapping pattern 3 with other overlapping patterns 3 using an automatic pattern inspection device using image recognition. , are compared with each other, and the pattern to be inspected 1 is inspected. In this way, a pattern to be inspected and a different reference pattern are superimposed to form a superimposed pattern, and since the superimposed patterns are matched and compared, no pseudo defects occur.

By the way, in the above embodiment, the thickness of the oxide film for forming the etching pattern was set at about 1000 mm, but this is because the thickness of the oxide film is about 1,000 mm. Any film with a detectable pattern after etching can be used. Furthermore, both negative type and positive type photoresists can be used, and photoresists to which dyes have been added can also be used. Also,
In the above embodiment, a contact hole pattern was used to align the overlapping patterns by image recognition, but the pattern is not limited to such a pattern. For example, the X-direction component necessary for alignment y
Any pattern may be used as long as it is composed of straight lines or curved lines that include both directional components. Furthermore, in the above embodiment,
The reference pattern is a pattern with a different shape from the pattern to be inspected. For example, if the pattern to be inspected itself includes both an X-direction component and a y-direction component, the reference pattern is set to a pattern with a pitch size that is 1 part of the pitch size of the pattern to be inspected. /n(n-
The pattern may be such that 2, 3...>1-/n. Further, as an exposure device for forming each pattern, for example, a reduction projection type exposure device is used.

As described above, the inspection method of the present invention improves pattern overlay accuracy based on image zero recognition and performs pattern comparison inspection with g accuracy without improving the mechanical accuracy of the stage of the inspection device. be able to.

In addition, it can be carried out using the close contact and etching methods commonly used in the production of semiconductor Wl, and the inspected semiconductor substrate can be reused any number of times by removing the resist pattern, without increasing inspection costs. This can contribute to improving yield.

[Brief explanation of the drawing]

The drawings are for explaining one embodiment of the pattern inspection method of the present invention, and FIG. 1 is an enlarged plan view of a main part of a pattern to be inspected, FIG. 2 is an enlarged plan view of a main part of a reference pattern, and FIG. 3 is an enlarged plan view of a main part of a reference pattern. is an enlarged plan view of a main part of a superimposed pattern. 1... Pattern to be inspected, 2... Reference pattern, 3.
・Overlapping pattern. Agent Yoshihiro Morimoto

Claims (1)

[Scope of Claims] 1. A reference pattern having a pattern different from the pattern to be inspected is formed on a semiconductor substrate, a pattern to be inspected is superimposed on this reference pattern, and this superimposed pattern is recognized as a pattern by image recognition. A pattern inspection method that uses an inspection device to compare other overlapping patterns formed on the same semiconductor substrate. 2. Claim 1, wherein the overlapping pattern is a straight line or a curved line including an x-direction component and a y-direction component in an x-y coordinate system necessary when determining a position by image recognition.
The pattern inspection method described.